In 2004, at age 30, Theo Epstein was the Red Sox’s wunderkind general manager when Boston ended its 86-year World Series drought. He was the Cubs’ president of baseball operations (and still is) in 2016 when Chicago ended its 108-year World Series dry spell.

That’s why Sports Illustrated named Epstein general manager of the decade, Fortune magazine declared him one of the world’s greatest leaders in 2017 and Time listed him among the world’s 100 most influential people. But I’m still more dazzled that Theo is the grandson and grandnephew of Philip and Julius Epstein, the writers of the screenplay for my favorite movie, “Casablanca.”

“I’ve probably seen ‘Casablanca’ half a dozen times straight through, and countless times I’ll stumble upon it in progress on TV and watch the rest,” Theo says. “It’s an amazing movie, but I’d be lying if I said the film itself has some great impact on me. When I see a reference to...